The present invention relates to a card edge connector, and particularly to a low insertion force (LIF) card edge connector.
Taiwan Patent Application Nos. 84218094 and 85219875 each disclose an LIF card edge connector including an insulative housing, a plurality of first contacts and a plurality of second contacts. Each first and second contact has a spring portion including a contacting portion which are located at different levels of the housing to generate a height therebetween. When a daughter card is inserted into the connector, an edge end of the daughter card first engages the first contacts having contacting portions proximate the top face of the housing and then engages the second contacts having contacting portions distal from the top face of the housing. Thus, the edge of the daughter card only engages half of the contacts at the same time thereby reducing the insertion force.
However, the spring portions of the first and second contacts have different lengths adapting for the height between the contacting portions thereof. While the daughter card is inserted into the connector, at least a first force and a second force being respectively parallel and perpendicular to a direction in which the daughter card is inserted in the connector are exerted on the first and second contacts by the daughter card. The first force buckles the contacts since each contact has a limited resiliency and is not able to withstand stresses exerted thereon. The second force produces a wear between each contact and a corresponding gold finger mounted on the end edge of the daughter card. The second force exerted on the first contact is different from the second force exerted on the second contact because the lengths of the spring portions of the first and second contacts are different in longitudinal direction. The difference between the second forces exerted on the first and second contacts results in different degrees of wear out between the first contact and the corresponding gold finger, and the second contact and the corresponding gold finger. Thus, one type of the first and second contacts is easily damaged than the other type of the first and second contacts after repeated insertions/withdrawals of a daughter card, which results in the connector being unusable while the other type of contact is still usable.
U.S. Pat. No. 5,201,663 discloses an electrical connector which comprises a first housing part, a second housing part and a plurality of contacts accommodated in the first and second housing parts. Each contact comprises a U-shaped contact spring portion received in the first housing part, a post portion or a leg portion held in the second housing part and an intermediate, resilient spring portion interconnecting the spring portion to the post or leg portion. The spring portion has a general S-shape to allow movement between the spring portion and the post or leg portion in three orthogonal directions. The first housing part is movable with respect to the second housing part when a mating connector engages/disengages the connector. The design of the S-shaped spring portion, however, does not concern a controlled bulking and a regulated contact normal force. Hence, an improved card edge connector is required.